There has heretofore been disclosed a double-side playing optical disk player which is equipped with two optical pickups so as to be able to play both the front and rear recording surfaces of an optical disk (referred to simply as a disk hereinafter) on a turntable without requiring an ejection operation of the disk. Such a double-side playing optical disk player has had a high cost due to the necessity of providing two expensive optical pickups.
In view of this, a double-side playing optical disk player in which a carriage carrying an optical pickup is guided by a drive guiding mechanism over both recording surfaces of a disk placed on the turntable has been proposed, for example, in Japanese Patent Application No. 61-130717. In this double-side playing optical disk player, the drive guiding mechanism employs first and second guide mechanisms disposed on both sides of the disk and which are freely movable in such a way as to permit the carriage to be engaged/disengaged at a prescribed engaging/disengaging position, and a transfer mechanism which transfers the carriage from the engaging/disengaging position of one of the first and second guide mechanisms to the engaging/disengaging position of the other mechanism.
In an optical disk player, a stable reproduced signal cannot be obtained unless the rotational axis of the disk and an extension of the moving locus of the optical axis of the projected reading light beam that accompanies the motion of the optical pickup along the recording surface of the disk intersect each other perpendicularly. In the prior art double-side playing optical disk player, the required orthogonality condition can be secured for one side of the disk, but maintaining orthogonality for the other side has proved difficult, and hence stable reproduced signals have not been obtained from both sides.
In addition, in an optical disk player, if the orthogonality relation between the disk recording surface and the projected light emitted by the optical pickup toward the recording surface is disturbed, distortion is generated in the shape of the pickup spot focused on the recording track being read, which causes leakage of information from adjacent recording tracks, giving rise to the phenomenon of cross-talk. Of the various causes that can disturb the initial orthogonality between the optical axis of the projected light beam and the recording surface of the disk, the most significant is the approximately bowl-shaped deformation generated by the contraction that takes place immediately after the formation of the disk. In order to reduce or eliminate cross-talk, it is necessary to provide a tilt servo mechanism which maintains orthogonality between the optical axis of the projected light beam and the recording surface of the disk.